Record Details
The ecology of parasite interactions within Chinook salmon
ScholarsArchive at Oregon State University
| Field | Value |
|---|---|
| Title | The ecology of parasite interactions within Chinook salmon |
| Names |
Hurst, Charlene N.
(creator) Bartholomew, Jerri (advisor) |
| Date Issued | 2014-08-07 (iso8601) |
| Note | Graduation date: 2015 |
| Abstract | The within-host interactions that can occur as a result of mixed infections in wildlife likely influence the outcome of an infection. We investigated the infection frequency and outcome as well as the potential mechanisms regulating mixed infections with two Ceratonova shasta genotypes within the Chinook salmon host. Previous research in our laboratory identified geographic areas throughout the parasite's range where multiple genotypes are sympatric and one area of particular concern where genotypes I and II account for the majority of the total parasites. We used sentinel fish studies to determine the transmission and persistence of both genotypes in Chinook salmon and found that both genotypes were transmitted to the fish host and that a majority (~80%) of initial infections were mixed. To investigate the outcome of mixed infections, we conducted a laboratory study that compared mixed and single genotype infections. Our results demonstrated that the production of mature parasites was reduced in mixed infections when Chinook salmon were exposed to both parasite genotypes simultaneously or genotype I first, perhaps facilitated by a truncated host life span that limited resources for genotype II. Interestingly, an initial exposure to genotype II eliminated competitive suppression and illustrated that prior residency favors the first infecting genotype. Next, using samples collected from the laboratory study, we investigated whether the immune response mediated the mixed infection interaction. The immune response to each genotype alone was specific and when infections were mixed, both genotype-specific responses occurred. Although the immune response to genotype II was associated with a decrease in genotype II density, the systemic immunosuppression elicited by genotype I prevented host recovery, suggesting the host immune response as one mediator of parasite interactions. Finally, we investigated the use of a less virulent genotype for host immunization against infections with a more virulent genotype. Although, our study demonstrated that immunization was unlikely, a number of study design variations remain to be tested. Taken together, these studies provide evidence for competition between C. shasta genotypes that is regulated by the immune response and by limited host resources. Understanding within host dynamics will better inform predictions of genotype re-distributions after barrier removal and fish stock reintroductions as well as parasite virulence evolution. |
| Genre | Thesis/Dissertation |
| Topic | Ceratonova shasta |
| Identifier | http://hdl.handle.net/1957/51648 |
